The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component that can be created using a fabrication process) has decreased.
The decreased geometry sizes lead to challenges in semiconductor fabrication. For example, as geometry sizes continue to decrease, the smaller critical dimensions (CD) and higher aspect ratios may cause difficulties in performing etching processes. In some situations, the etching process may inadvertently or unintentional etch away an excessive amount of a layer that should not be etched. When this occurs, the result is degraded device performance or even device failures.
Therefore, while existing semiconductor devices and the fabrication thereof have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect.